Curved closure device



March 18, 1958 P. GRAHAM CURVED CLOSURE DEVICE Filed June 24, 1953 INVENTOR Phi/lip Graham FIG. 1

Affarny United States Patent 2,826,787 CURVED CLOSURE DEVICE Phillip Graham, Pittsburgh, Pa.

Application June 24, 1953, Serial No. 363,867

22 Claims. (Cl. 20-35) An object of my invention is to provide a low cost,

strong, durable, attractive door or the like, able toresist destructive forces, and which will resist deterioration from exposure to the elements.

Other objects of my invention are to provide substantially improved doors or the like, which will become more apparent from the following description taken Withthe accompanying drawing wherein:

Figure 1 is an elevational view of a curved door.

Figure 2 is an enlarged fragmentary sectional view taken along line 22 of Fig. 1.

Figure 3 is an enlarged sectional View through a resilient seal-cushion shown in Fig. 2.

Figure 4 is an enlarged fragmentary sectional view taken along line 44 of Fig. 1.

Figure 5 is an enlarged fragmentary sectional view taken along line 5-5 of Fig. 1.

Figure 6 is a schematic diagram, showing the control of distortion along'the width of the door shell.

Figure 7 is an enlarged fragmentary sectional elevational view taken along line 7-7 of Fig. 1.

Figure 8 is an enlarged fragmentary sectional view taken along line 8-8 of Fig. l.

'sist high exterior pressures.

ICC

gives'the impression of strength and beauty. It is, in general, symmetrical about its vertical axis except for the hinges and lock.

This curved door would require less material than would common flat doors of equal strength.

The door shown in Fig. 1 is illustrated as an exterior door with the arched shell bowed to the exterior to re- This would be an exceptionally sturdy door arrangement, capable of resisting h forces from abnormal conditions, such as exterior explosions in wartime or peace, high winds from hurricanes, force of tidal and fresh water fioods,'force of avalanches, forcible entry of undesirable persons or animals, and impacts from missles carried by the force of explosions and winds. A continuous, resilient, sealed cushion around the edge of the door prevents the passage of insects,

rodents, dirt, fumes or odors, moisture, sound, light, heat,

cold, smoke, tidal or fresh waters; and, since it would retard the progress of fire, it is a fire seal. It seals in air for air-conditioning. In wartime, this seal on the door would prevent the passage of warfare types of poisonous gas,

- smoke, bacteria, and radioactive dust or mist from an Figure 9 is an enlarged fragmentary sectional view '7 to Fig. 4 taken through a modified form of door, showing a modified panel across the chord.

Figure 13, Figure 14, and Figure 15 are fragmentary sectional plan views, similar to Fig. 4, taken through further modified forms of doors.

Figure 16 is a reduced elevational view, showing a modified form of door shell with localized corrugations.

Figure 17 is a fragmentary sectional plan view taken through a further modified form of door or closure.

Figure 18 is a sectional view taken along line 18-18 of Fig. 17.

Figure 19 is a fragmentary sectional plan view taken through'a further modified form of door or closure.

In general, the door or closure device shown in Fig. 1 is light-weight, strong, and durable. It is relativelyflow in cost to, build, install, and maintain. The curved door atomic blast. The seal will yield to break away from ice that forms around the door. A door equipped with an edge cushioned-seal closes noiselessly even when slammed hard. The seal-cushion would also yield to take up the slack caused by discrepancies in the door or door opening. Thus, a less accurate door and door opening is required; therefore, an accurate costly door frame or door opening is unnecessary. There would evolve no future door trouble caused by slight settling of the building and untrued door openings'due to the settling. v

Curved door shell 1 is bowed in width to create an arch. This shape is strong, to resist pressure on the convex side of the arched shell and to allow for expansion and contraction in the shell without objectionable warping or cracking. The curved shell 1 has a shape with a high section modulus. to prevent bending lengthwise, caused by exterior pressure or minor stresses resulting from expansion and contraction due to differences in temperature or moisture in the door parts. An exterior thrust against the arched shell 1 is transmitted through the shell to the door jambs or wall effectively.

Since possible loads on the convex surface of the arched shell effect compression in the arch, the door shell 1 may be constructed of materials that are strong in resisting compression, such as metal, plastics, or laminations of these and/or other suitable materials. The door, if of plastic, etc., may be reinforced with metal, fiber glass, or other suitable reinforcing, impregnated in the door material. A metal or plastic shell may have wood, cork, and other relatively weak materials laminated to it, for appearance and for insulation.

Referring to Figures 1, 2, 4, and .5, looped sides 1d of the shell 1 are shaped to form a trim and to stiffen the sides of the door. Shell 1 is welded, riveted, or otherwise fastened where it closes the loop 1d. The top and bottom ribs 4, and the intermediate ribs 5, stiffen and help to hold the curved shell 1 to a bowed shape. The ribs 5 may be omitted when possible loads are light. The ribs are shaped to allow controlled outward expansion and inward contraction throughout the width. of the shell 1. Hinges 6 and lock 7 of any suitable type are placed to suit the door. The hinge reinforcing plate 6a (see Fig. 5) is used when a thin shell 1 requires reinforcing. A11 intermediate rib 5 is shown in Figs. 2, 4, and 8. Figures 5, 7, and 9 show ribs 4 which are similar to ribs 5. The ribs are connected to the shell 1 by fasteners 8 which may be rivets, bolts, or welds if the door is made of easily welded material. Curled rib flanges 4a and 5a stiffen the ribs, cover the adjustable wire ties 10 and act as trim, Other suitable shaped flanges may be used if desirable. Wire 10 restrains the arched door width from spreading and flattening under normal conditions.

to the jambs, the wire 19, which has a coiled spring as showrrnear the center in Fig. 2, yields when a greater force on the door shell flattens the arch slightly and causes the direction of the thrust to be exerted into the door jambs in an approximate straight line from the arch. This allows the walls to take the thrust more nearly 111 When conditions are such that after a force on the exterior of the door shell has tightly seated the door the direction of the length of the wall, whereas conventional door stresses tend to cause shear and bending in walls and partitions. Thus, less sturdy walls or partitions can be used to take the thrust from the curved door.

When conditions are such as those with weak short walls, and it is not desirable to divert the additional thrust onto the wall from the door, the tie wire 10 may be used without a coil spring in it; or a link (not shown) may be placed astraddle the coil to take the thrust and to thus prevent the spring from yielding. Interior doors that are not subject to heavy forces may have non-resilient tie wires 10 without the coiled spring. These ties it) are covered by the ribs, etc., to protect them from corrosion and for appearance. One or both ends of wire 19 may be threaded. As shown in Fig. 4, a nut 10a is turned for adjusting the effective length of the wire 16, to maintain the desired door width. Modified ties to act in place of wires 10 may be used, such as a tie shown in the modificationillustrated in Fig. 13 whichwill be described in detail hereinafter. A reinforcement 10]) at the end of each rib, see Fig.4, may be used to prevent puncturing of the thin shell 1.

The edge of the rib contacts the shell 1 only at spaced points near the fasteners 8, and at the ends. Between the fasteners 8, and between the ends and fasteners 8, the ribs 4 and 5 are flanged and cut back from the centour of the shell 1 to. allow gaps 4b and 5b, which allow local flattening during the contraction of the shell 1. These gaps may be left open between the shell 1 and the ribs; or, if desired, a resilient filler 11, such as one made of resilient rubber, felt, or plastic, may be used as a gap filler. To hold the filler 11, the flanges on the ribs are grooved slightly to form a keyway for keying the filler 11 securely. When desirable, in modifications, only the gap 4b at the bottom rib 4 may have the filler 11 inserted to prevent dust and dirt accumulating in it when a resilient cushion-seal 12 is used. If an exterior door of this type is made without the seal 12, the filler 11 would be useful at the top and bottom ribs to insulate against moisture, air, sound, etc.

Where the ends of the door ribs 4 and 5 are adjacent to the sides 1d of the shell 1, adjustment is made to maintain the correct door width by trimming down the rib ends or by shimming or wedging. Wire is used as a take-up in adjusting the width of the door. When the sides 10' are to transmit only enough of the thrust from the door shell 1 to the door jambs to seat and seal the edges, the ties without a yieldable arrangement are used to take the thrust from the shell 1. The top and bottom of the door may then transmit most of the load to the floor and the ceiling. The door may be hinged to or near to the floor and ceiling.

The seal-cushion 12 is fitted onto the dovetailed scalloped edging 1e (see Figs. 10 and 11) around the door perimeter. It acts as a seal, a cushion, an insulator, and a trim. It hides'the holesfor the ends of wires 10, etc. The seal 12 may be made of attractive colored material. On a modified door without a seal, the scalloped edging 16 may be omitted. Seal 12 acts as a cushion on the door, allowing it to close silently. Pressure on the outside of shell 1 has a tendency to compress the seal 12, thus creating a larger seal bearing surface with the building wall. With higher pressure on the door shell, the seal becomes flatter and tighter. Thus the thrust from the .4 door shell 1 is evenly. distributed to the door jambs or wall, as the resilient seal 12 overcomes small discrepancies in the door opening and the door, which would otherwise prevent a good bearing surface. Since the seal 12 would allow more tolerance in hanging the door than is possible with ordinary flat doors, the present door can be more easily and quickly erected.

ln modifications (not shown) the seal 12 and the filler 11 at the top and/or bottom of the door may be combinecl.

In another modification (not shown), the seal with or without the filler may be used at the top and bottom of the door without the seals 12 along the door sides, the loops 1d bending slightly to act as a limited seal, or the seals may be on the door opening, such as that shown in Figs. 14 and 15.

The door opening, formed by wall 13, is indicated by a dot-dash outline. Door jambs are shown beveled to receive the seal 12, and thus the thrust of the door. The door jamb shown has an offset to prevent visibility from either side through any slight crack along the door sides. The threshold is shown in Fig. 9; seal 12 bears against it. The lintel above the door, formed by the building wall, is shown in Fig. 7. It is projected out from the wall to divert the rain from the door opening. The hinges 6, shown in Figs. 1 and 5, may have resilient straps, such as those of spring steel, to allow them to bend readily when high pressures are exerted on the convex surface of the door. Thus the load may be transmitted through the door edges to the wall, rather than through the hinges 6. The hinges 6 allow the seal 12 to compress slightly when the door is closed. The hinges 6 may be grouted to a masonry wall after the door has been set accurately, or fastened to the wall if the wall is made of wood. The hinge pin holes may be slotted to allow the hinge to yield when the door flattens slightly when under a heavy load. The latch on lock 7 engages a suitable slotted catch on the door jamb to allow the door to move in to bear tighter against the wall when outside pressure is increased.

The swing of the door may be reversed in modifications (not shown), especially where weather resistance is not required. Either side of the perimeter of the door may be modified to fit conventional door frames, with or without a door seal.

Figure 6 is a schematic diagram showing the distortion of the door shell 1 along its width, which results from expansion and contraction. The solid curved line In indi cates the normal contour of the door shell. The fixed points 8a are located at the ends of the ribs and at the fasteners 8. The flanges of ribs 4 and 5 may be welded together at fasteners 8, where they were cut and bent to touch; and/or a reinforcement such as a bent reinforce ment or grommet that is shown, may be used to help make a suitable riveted connection. The fasteners 8 divide the shell bending area into three small incremental areas or zones. In modifications there may be more or fewer bending zones (not shown) than three. Bending zones allow unobjectionable bending in the arched shell 1, without causing undesirable warping of the door. The door shell 1 bends locally in width and the strong curved shape restrains it from bending lengthwise. The door shell is restrained from spreading by the ribs, ties, and door jambs. When the door shell 1 expands due to increased temperature or increased moisture, if absorbent material is used, such as wood veneering laminated to metal or plastic, it takes on the bulging contour in the bending zones between points 3a, shown by dashed line 1b. The cooling of all doors, and drying out in wooden doors, causes contraction which, Without this localization of bending, causes undesirable warping and cracking. The curved shell 1 allows the curved width to flatten out locally in the bending zones for contraction. When the door shell 1 shrinks, it assumes the contour indicated by dotdash line 10 in Fig. 6, which flattens between points 8a.

I Ribs in the door may act as shelves, when slats 21 (only one being shown) are placed above the ribs to keep articles from falling off. This arrangement would be practical for closet doors, bedroom doors, and bathroom doors. Shoes and other items could be stored in the shelves and still be accessible. A window 22 with a resilient frame may be placed in the shell. A resilient window frame would allow for bending in the shell and still maintain a seal. A resilient frame with jalousies or louvers (not shown) may be placed in an opening in the door shell.

A mail slot 23 with a resilient seal may be placed in the shell. A cross slat 21 below the mail slot, would help form a rack to catch the mail.

A bathroom door may have towel hangers 24 (only one being shown) attached below the ribs.

The interior or fiat side of the door may have a suitable panel or covering 20. It may be a stiff or a relatively weak covering of cloth, etc. It may be a mirror or it may be an insulating cover. The panel 20 may be hinged to form a closet space in the door.

Various types of insulation 2 may be used. Insulation material may be inserted to fill up the whole cavity in the door or insulation material of uniform thickness may be used similar to that shown in Figs. 17 and 18. Sand and water may be the insulator inserted in such a door as an insulation or barrier against the heat and harmful gamma rays emitted by atomic explosions. The sand may be kept in the door, and the water added when an emergency existed.

While I have shown a door in Figs. 1 to 11 inclusive that is suitable for metal construction, a door with the same principles, such as the yieldable ties, may be made with thicker members, such as wood, plastic, concrete, etc., as described in my copending application Serial No. 265,465, filed January 8, 1952, entitled Curved Closure Device.

Figure 12 shows a modification of a door that is similar to the arrangement shown in Fig. 2. A modified panel 20a, which is similar to panel 24), has its side edges curled for stiffness and appearance; and the edges offer more resistance against the ribs puncturing the shell 1, and thus reinforcements 101) may be omitted. The panel 20:: may be incorporated into the door after it has been in use by disconnecting the wires 10, etc., trimming the ends of ribs, or removing reinforcements 1%, inserting panel 24in by bowing it slightly and reconnecting ends of the wires 10.

Figure 13 shows a modification which is similar to the arrangement shown in Figs. 1 and 4. A side piece 14, such as an extruded section, stittens the side edge of the door and may be used instead of the looped side 1d. The side piece 14 engages the edge of the modified curved shell 1g, which is similar to the curved shell 1. The shell 'lg has the scalloped edging 12 to form a dove-tail shape to engage the dove-tailed groove 140 in the side 14. After this dove-tail joining of the parts, the joint may be pressed to tighten it; and it may be cemented or welded tight, such as by resistance welding. The side 14 has a dovetailed projection 14!) to engage the seal-cushion 12. It also has a projection 14a to form a trim and to hold a panel 20. The panel'20 may be added before or after the door has been in use, or it may be omitted. A panel, such as 20a in Fig. 12, may be used in place of panel 20.

The arrangement shown in Fig. 13 would have holes in alignment to take the adjusting screw 100. The projection 14b may be notched for entering the screws 100. The nut c bears against the spring 10 The spring 19 bears against a washer which is held by fingers punched into the rib or otherwise held. The resilient wire 10 may be omitted if the rib alone can carry the tension stress. The spring 10 will compress to make a yieldable tie under a great load. Other means for tieing the sides together may be used, such as the arrangement shown in Fig. 2.

A modification of the arrangement shown in Fig. 13 may include a shell that does not have scalloped edging along its sides. The side edges would fit into a suitable groove in side members similar to the sides 14. After insertion, these may be pressed together and it may be fastened, such as by resistance welding or riveting.

A modification of the arrangement shown in Fig. 13 may omit the seal 12.

Figure 14 is another modification which is similar to the arrangements shown in Figs. 1 and 4. A curved shell 11; is similar to shell 1. It has loops 1k at the sides to form suitable stiffening and to offer a bearing surface against the door opening. The edge of .the shell 1h has riveted, welded, or other type of connection 1m to close the loop 1k. There may be a resilient seal-cushion 25 in the door opening, so the door will bear againstit to form a tight closure. The other modified doors without seals on them may be used with a seal in the door opening. The seal 25 may be omitted, with the looped end 1k forming a slightly resilient arrangement so as to maintain a limited seal and act as a liimted cushion. The top edge of the shell 1h may have scalloped edging 1e to receive a seal, such as. seal 12.

A suitable take-up would be used to tie and adjust the door width, etc. A similar tie to that shown in Fig. 13 is shown. It has a beveled washer under the screw head. In a modification, a tie similar to that shown in Fig. 2 may be used. The panel 29a may be omitted. If a panel is used, a panel 20 (not shown) may be used in place of the panel 20a.

Figure 15 is another modification which is similar to the arrangements shown in Figs. 1, 2, and 14. The curved shell 1] is curled or curved along the sides. There is a seal-cushion 25 in the door opening. it may be omitted when a seal is not needed. A seal may be used along the top and bottom similar to that for the shell 1. The panel 20a may be used, or a panel 2%) (not shown) may be used.

Figure 16 shows a modified curved door shell 1p. It is similar to the other curved door shells described except that it is pressed or embossed locally to form corrugations for stiffness. Other patterns than the corrugations shown may be used for stiffening the door. A door shell with corrugations similar to the shell 1p may be used in modifications of the doors previously described.

Figure 17 shows a modification of the door or shutter shown in Figs. 1 and 2. It has a corrugated curved shell 11'. The sides are looped the same as the sides id for the shell 1. V

Figure 18 is a sectional elevation through this type of door. The corrugations are deepest at the center of the door width, and they taper to zero near the ends of the arch. These stiff corrugations prevent the buckling of the thin shell from exterior loads. The shape of the shell 11' makes it strong for its weight, as compared to that for conventional flat doors or shutters. The seal 12 may be omitted when conditions do not require it. A tie wire 10 may be used or be omitted, depending upon the loading conditions for which it is used. A strut 26, which is shown as a tube around the tie wire, may be used to keep the shell 1r spread. When the shell 1r is made to bow out slightly from its true shape, the strut 26 may be omitted. When a yieldable tie is not desirable, the ends of strut 26 may be fastened securely to the sides of the shell. When a shell 1r is accurately shaped to size, it may be used effectively without ties 10 or struts 26. Once it has seated to the door opening by a force on its convex surface, it will bind; and then, when the force on it is increased, it can flatten slightly to transmit the load intothe door jambs in an approximate straight line from the arch. The threshold and the under side of the lintel are curved to match the curvature of the door or shutter. Insulation 20. may be a bowed piece of insulation board.

When a cover 2%, such as that made of sheet metal or a 7 plastic is used, other types of insulation may be used the same as described for the door shown in Fig. 1.

Modifications of the door or shutter shown in Figs. 17 and 18 may be made without the seal-cushion l2; and a seal-cushion (not shown), such as a seal shown in Fig. 14, may be placed in the door opening to form a seal-cushion arrangement.

Figure 19 shows a modification of the doors or closures shown in Figs. 1, 4, 17, and 18. It has a corrugated curved shell 1:. The corrugations are deepest at the center of the door width, and they taper to zero near the arch ends. A dove'tailed shaped edge around the perimeter of the door is a means to attach a cushion-seal 12. The corrugations in the width of the shell 1t make it strong to enable it to carry loads to the door jarnbs. The non-corrugated side edges with the dove-tailed shape stifiens the closure lengthwise. This strongly shaped closure, when made of suitable materials, does not require tie wires or struts. After it has seated from the force on its convex surface, any slight flattening of the shell from an increased force on it would allow the door to slightly yield in width across its chord to direct some of the thrust from the arch into the door jambs in approximatcly straight lines from the arch ends. Glass or plastics that are strong in compression and shear are suitable materials for this type of closure. This type of shell may be reinforced with wire it of glass, and with wire, fiber glass, etc., if of plastic. Laminated shells of various desirable materials to suit conditions where it is to be used, may be made in this shape. in modifications, insulation similar to insulation 2a shown in Fig. 17 may be attached. Transparent or translucent types of glass and/or plastic may be used. The glass may be tempered to increase its security value. Since a glass closure as shown is strong in its ability to withstand shear and compression, and, after it seats under a load, it is trapped so that it can yield or bend only slightly under additional loads, it would be highly suitable for protection, when it is desirable to have strong, durable, beautiful, and translucent closures.

A similar closure modification to that shown in Fig. 19 may be made without the seal 12. A seal, such as seal 25 shown in Fig. 14-, may be used when the seal 12 is not used.

While doors bowed in width only are shown, it will be apparent that they may be bowed also in height, or in height as well as width.

While I have shown and described the closure shown as suitable construction for thin metal or plastic doors, etc., much heavier similar closures with shells of wood, plastic, glass, or concrete of similar construction may have the yieldable ties.

The door shown in Fig. 1 and modifications of it, such as those shown in Figs l2, l3, 14-, 15, and 16, would be highly desirable if they were made of aluminum, as they would be light in weight, so they may easily be handled and erected even by a person frail in build, shipped at low cost, and the light weight door would require smaller hinges and supports for the hinges compared with conventional heavier doors. Storm doors or shutters of this type could be stored in quantities in a small space without overloading the floor. Aluminum does not readily corrode in many locations, and thus does not require paint under many conditions, and it can be coated to resist corrosion when necessary. Aluminum is not affected by pure atmospheric moisture which causes wooden doors to warp and unprotected steel doors to rust. Aluminum color is attractive, and aluminum may be colored to change the appearance. Aluminum door is resistant to fire, rodents, vermin, ctc. Aluminum would be particularly suitable for closure devices such as those in warm climates where destructive elements are prevalent. Permanently fixed doors and shutters, such as those of aluminum, may be used and closed when hurricane winds must be kept out of buildings. A metal door,

a particularly an aluminum door, would add to the sanitation conditions in a building as vermin cannot eat it or readily hide in its parts, and it can be readily cleaned.

The doors may be made of carbon steel, etc., which has .suitable protective coating. Where highly corrosive elements are at times present, the closures may have a stainless steel or other corrosive resistant shell and the ribs, etc., of suitable materials. Stainless clad sheets may be used for parts on these doors.

The doors shown may be made very light in weight when not subjected to wind pressures, etc., and they would therefore be particularly suitable for closet doors or any door that needs only to act as a screen and to keep out dust and other minor destructive elements.

in general, these closures when made of sheet metal would, by their shape, be strong even though they are of thin metal.

A series of these closures may be placed edge to edge and securely fastened to form barricades against destructive elements, such as wind, water, mobs, etc.

Thus it Will be seen that I have provided an eiiicicnt and strong closure element, in the form of a door, shutter, or the like, which provides optimum strength for a given weight; and which, by curvature of panel, makes it possible to withstand abnormal wind forces; also, I have provided novel ribs for such closure element which have spaced anchoring points across the width of the closure element, and between which anchoring points a small space is provided between the curved panel of the door and ribs so as to permit free outward or inward bowing of the panel portions, such as caused by temperature or humidity changes, thereby providing uniform distribution across the width or" the closure element of such bowing. Also I have provided a closure element, having yieldable tie members, so as to form a tight seal when subjected to loading, such as from excessive wind. Additionally, I have provided a closure element which may be made of aluminum, steel, plastic, or other suitable materials and which may be provided with a resilient sealing material about its perimeter and the interior of which may be filled with insulating material.

While 1 have illustrated and described several specific embodiments of my invention, it will be understood that these are by way of illustration only, and that various changes and modifications may be made within the contemplation of my invention and within the scope of the following claims.

I claim:

1. A closure device comprising an outwardly curved thin panel, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface; and a plurality of ribs, each having spaced anchoring points secured to one side of said panel and allowing said panel to freely expand or contract at intermediate portions between said anchoring points.

2. A closure device comprising an outwardly curved thin panel, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface.

3. A closure element comprising an outwardly curved panel, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface, a plurality of transversely extending ribs secured to said panel in spaced parallel relationship, each of said ribs having spaced projecting portions which are anchored to transversely spaced portions of said panel, there being a space between the intermediate edge portions of said ribs, between said projecting portions, and the panel so as to allow contraction of the panel as the result of reduced temperature without obstruction from said interof substantially rectangular shape and bowed, across the width of the door, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface, a plurality of ribs secured to said panel in spaced parallel relationship, each rib extending across the width of the door, each of said ribs having spaced projecting portions which are anchored to said outwardly bowed door panel and between which spaces are provided for allowing free outward or inward movement of the door panel portions which extend between said anchoring projections.

5. A door comprising an outwardly bowed panel, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface, a plurality of spaced parallel ribs, each extending along the width of the door, and each provided with a plurality of angularly disposed edges facing said panel and providing corners which are anchored to spaced portions of the panel along the width of the door, and a flat panel spanning the concaved face of said panel and secured to one of the edges of said ribs, whereby the outwardly bowed panel may freely expand or contract between said anchored corners as the result of temperature changes.

6. A closure element comprising an outwardly curved thin panel, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface, a plurality of transversely extending, spaced parallel ribs, .each having projecting portions which are secured to transversely spaced portions of the panel, and

a strip of resilient material surrounding the perimeter I of said outwardly curved panel.

7. A closure element as recited in claim 6 wherein a cavity is provided within said resilient material and which extends throughout the entire perimeter.

8. A closure element as recited in claim 3 wherein the space between said edge portions of said ribs and said outwardly curved panel is filled with yieldable material.

9. A closure element as recited in claim 5 wherein yieldable heat insulating material is provided in the space between said flat panel and said outwardly bowed panel.

10. A closure element as recited in claim 2, together with a pair of hinges of yieldable material for hinging said closure element to an opening in a building wall so as to allow an edge of the closure element to bear against an edge of said opening.

11. In a building wall having a rectangular opening for a door, the sides of said opening being beveled outwardly in the direction of opening of the door, in combination, a door having an outwardly curved, thin panel, the perimeter of which bears against the sides ofsaid opening to form a seal therewith, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on opposite sides thereof, to permit said device to expand in width when pressure is applied to its convex surface.

12. A combination as recited in claim 11, together with a strip of resilient material surrounding the perimeter of said door for providing a seal with said opening.

13. A closure element comprising an outwardly bowed panel, a plurality of yieldable tie elements disposed in spaced parallel relationship for maintaining said outward bow of said panel, each of said tie elements having its extremities secured to opposite portions of the width of the panel, a thin fiat panel secured to said tie elements,

and a filling of heat insulating material, between said fiat panel and said outwardly bowed panel.

14. An outwardly bowed closure element for a wall having'a rectangular opening, said closure element having corrugations extending transversely throughout a substantial portion of the width thereof exclusive of the side portions, the sides of said closure element being seatable againstsaid opening and yieldable tie elements connecting the opposite sides of said closure element to permit the width of the closure element to increase as a consequence of pressure applied to the outer bowed surface thereof.

15. In a wall having a rectangular opening, an outwardly bowed closure element having corrugations extending transversely throughout a substantial portion of the width thereof exclusive of the side portions, the sides of said closure element being seated against said opening, and yieldable tie elements connecting the opposite sides of said closure element to permit the width of the closure element to increase as a consequence of pressure applied to the outer bowed surface thereof, and a seal disposed between the said opening and said closure element.

16. A barrier comprising a thin, substantially rectangular panel bowed outwardly into a convex shape from a plane defined by a pair of opposite sides and being straight in cross section in a plane at right angles thereto, a plurality of yieldable tie elements whose extremities are fastened adjacent said opposite sides to permit said barrier to yieldably expand in width when pressure is applied to its convex surface, and a plurality of ribs extending between said sides, each rib having spaced anchoring points secured to the concave side of said panel and allowing said panel to freely expand or contract at intermediate portions between said anchoring points.

17. A barrier comprising a thin panel curved outwardly into convex shape from a plane defined by opposite sides thereof and being straight in cross-section in a plane at right angles thereto, a plurality of yieldable tie elements whose extremities are fastened adjacent the extremities of said panel on said opposite sides, to permit said barrier to yieldably expand in width when pressure is applied to its convex surface.

18. In a building wall having a rectangular opening with outwardly beveled sides, a thin rectangular closure element bowed transversely outwardly into convex shape from a plane defined by opposite sides of said element and being straight in cross-section in a. plane at right angles thereto, said closure element having corrugations extending transversely between said sides throughout a substantial, intermediate portion of the width thereof but said sides being devoid of corrugations, said corrugations progressively diminishing in height from the center of said element to points short of said sides, the sides of said closure element being seated against said opening, whereby said closure element will yield in width without buckling when pressure is applied to its convex surface.

19. A closure element for closing a building wall having a rectangular opening with outwardly beveled sides, said closure element being bowed outwardly of said opening in a transverse direction only and having corrugations extending transversely throughout a major portion of the width of said element, said corrugations diminishing in height from the center toward the sides of said closure element and being of Zero height at said sides, and a seal attached to the sides of said element which is adapted to rest against opposite sides of said opening, whereby said closure element will partially flatten in curvature and yield in width so as to compress said seal when'pressure is applied to its convex surface.

20. A closure element as recited in claim 18 together with yieldable tie elements connecting said opposite sides thereof to provide yieldable resistance to said element as it expands in width.

1 1 21. A closure element as recited in claim 18 which is 2,050,070 made of plastic material. 2,208,198

22. A closure element as recited in claim 18 which is made of transparent plastic material.

5 719,456 References Cited in the file of this patent 207,740

UNITED STATES PATENTS 1,895,553 Nordell Jan. 31, 1933 12 Smith Aug. 4, 1936 Seaman .a July 16, 1940 FOREIGN PATENTS France Nov. 14, 1931 Switzerland Mar. 1, 1940 

